c# WPF Line and Column number from RichTextBox

Something like this may give you a starting point.

TextPointer tp1 = rtb.Selection.Start.GetLineStartPosition(0);
TextPointer tp2 = rtb.Selection.Start;

int column = tp1.GetOffsetToPosition(tp2);

int someBigNumber = int.MaxValue;
int lineMoved, currentLineNumber;
rtb.Selection.Start.GetLineStartPosition(-someBigNumber, out lineMoved);
currentLineNumber = -lineMoved;

LineColumnLabel.Content = "Line: " + currentLineNumber.ToString() + " Column: " + column.ToString();

A couple things to note. The first line will be line 0 so you may want to add a + 1 to the line number. Also if a line wraps its initial column will be 0 but the first line and any line following a CR will list the initial position as column 1.